Radiographic process



June 20, 1950 A. H. J. DE LASSAUS s'r. GENIES 2,512,242

RADIOGRAPHIC PROCESS Filed July 24, 1947 dun. m V Inventor.

Attorney;

' companying drawing.

Patented June 20, 1950 UNITED STATES" PATENT OFFICE namocnarnro PROCESS Anne H. Jacques de Lassus St. Genis, Versailles, France Section 1, Public Law 690, August s, 1946 Patent expires September 11, 1964' In radiography it is known to make radiographic sections by displacing the radiogenic source and the radiographic plate during the time of the exposure by parallel movements in opposite directions relatively to the subject being radiographed, such that the respective amplitudes of these displacements are in the same ratio to one another as are the respective distances of the source and the sensitive plate from the plane containing the section required. It is also known in photography to record a" and at the same time are capable, when desired,

of exhibiting such subject in correct relief and also its changing aspect with the change in viewpoint of the observer; to provide methods and means for recording and viewing such radiog'raphic negatives and copies thereof; to provide methods and means for recording multiple radiographic sections and multiple radiographs on the same negative, and for viewing these by one or more observers at a time; to provide novel screen devices for recording purposes, and other objects and advantages of the invention as will become evident in the ensuing 'description and ac- In the accompanying drawing: I V I Fig. 1 schematically illustrates the recording j process.

Fig. 2 is a schematic detail in section on an enlarged scale of the elementary chambers'produced by the lined screen or by the translucent lenticular screen on the emulsion of the original In Fig. 1, L represents the displacement of the Iadiogenic pin-point source S, K represents the.

2 Claims. (01. 250-65) stationary subject to be radiographed, XX indicates the plane of the radiographic section (perpendicular to'the plane of the drawing) to be produced, and T, P represents the movable assembly or system comprising the lined screen (or grid) T and the sensitive emulsion support P, which undergoes the displacement represented by E.

If h and d are the respective distances oi the line I, 2 of displacement L of the source S from the plane of displacement E of the system T, P and from the plane XX of the radiographic section to be produced, there exist three simple relations characteristic 0f the process between the magnitudes E, L, h and d;

F hd

which expresses the ratio of the parallel displacements in opposite directions of the sources and of the emulsion support P provided with its grid T, in order to obtain the section'on the plane i v h' L+E which expresses the homothetie relation existing between the dimensions-of the subject K and those of the spatial image K or Kfof the subject observable in its three dimensions on the developed negative (or on any copy made by contact from such negative) when provided with a viewing screen or grid of the same pitch p as the recording grid T.

With the grid T of pitch p at a given distance a from the emulsion surface I (Fig. 2) of the negative P, it can be shown that, for each point such as A, B, C belonging to the subject K, there will be recorded on the emulsion I by the sweeping of the pencils through the angle 9, areas of unequal extent such as (a1) as, (b1) b2, (01) 02, composed of point images regularly spaced at intervals greater or smaller than the pitch of the grid T, according as to whether the points belonging to the subject are situated nearer to (such as A) or farther from (such as B) the line I, 2 or.

displacement of the projection point S, than the section plane XX. For any point C such as which is situated in this section plane, a single point trace is recorded on the emulsion I.

These arei the. recording conditions. which make it possible, with the aid of a viewing lined screen or lenticular screen of the same pitch p as the recording grid and of the same orientation and at the same separation E relatively-itowthedined image on the developed originalnega'tive (or on contact copies made therefrom) to examine the image K" (Fig. 1) of the subject K in relief with the change of aspect accompanying ,thewchange of the observers viewpoint, moving,for instance, along the whole base LE comprised between the points 1 and 2 relatively to the negative. if .a lenticular screen is used for viewing (as indicated in dotted lines in Fig. 2), 6 denotes %-the ;focal length of its elementary plano-convex lenses.

However, as -;-in radiography the subject K is necessarily placed between the point projection source S and the ;emulsion-suriac;e I rip-ring resendin w reas nzc c os p ywh e rd ;a photograph in relief it isthe projection point 'anam y. thelemersen lhcsi co c h chictive) --which is placed between the subject and the emulsion surface, it will be appreciated that in t prese t thc :ror e h oeraph c -:nesat ve can onl b v wed. an see e f, 1 h -sam -sense the-subject when the'negative iis fitted with a dined screen or denticular screen, gelatinised {layer towards {the screen, ex-

'iactly as the an inane ativ wwas a ran ed 55 viewing screens-ibis necessary toturn each copy over before fitting it with-its screen, if the thickness of the emulsion support permits, that is to say, if this thickness is of the order of e. vlt -will readily be appreciated that a variation of produces a proportional variation in the same sense as E of the scale of the spatial construction presented to view.

The influence of thethickness of the copies is, therefore, not appreciable if they-areon film. Owing to the slight'thielrness pf-the support. Any difliculty in this respect disappears altogether if the original is recorded with the support side, and not the emulsion side, against the recording rid messag n s which defines i a EQPI iQ b n e n n thi caress in th r vio @1- te em t t e a n b tw en t e emul e 511119439 an $1 zord hg-e i du n fiiq i'i li Th mo 9 le s atpermeahilii .Q e' ars number of materials to vthe raysemitted ,by the adios s um re i s r n ur n g o e -..ravsi n xcmn nthc angles as defin d by the second of the characteristic relations a ove 4 noted lies between 20 and 30, the ratio of the height of the bars to their base (of a width approaching the pitch p of the grid) is of the order of 2. If, for example, the pitch of the grid is 5 rofqni'llimetre order (-e. ;g.,-12 to ,16 bars to the centimetre), which is quite permissiblefor radiographic negatives having dimensions 18 x 24 om. at least, radiographic negatives being always 7 of lower definition than photographic negatives, 10 the height of the bars will be sufiicient to presemen-effective opacity to the rays reaching the emulsion after passing through the subject to be ra ioerep esllllustratively, Fig. 3 shows a grid of this kind spaced at a distance 6 from the emulsion surlfaqegh of anunexposed negative P1, the wider base of the opaque bars G1 being flush with the .facepf the grid plate T1 which faces the emulsion layer I1. In this embodiment, the grid plate I1 -is supportedin the requisitespaced-relation :byany suitablemeans (not shown), suchsasa frame of calibrated thickness.

,In the arrangementishownin Fig. .4, the-spacings is provided by the thickness of thenegative B2 itself,-which is interposed between the-grid plate (IT-z and the-emulsionrlayerlz so that the latter is underneath.

In-Fig. 5-the grid plate Iifaces the emulsion side liofthenegative Psiandthe spacingis pro-- vided in ,this; case loy an extra thickness. of l the material-of the-plate T3 itself which covers the wider base of .the4bal3sG3-andis interposed be tween them and the .emulsionlayer Is.

In theembodiments of Figs. 3 and 4,,recesses ,orqgrooves ;-in the ,gridplate T1 or -T2 for accommndetins vt inlaid bars $1 --.or 2 m y be pro- ,duced with ,a machine .tool ,of ,theengravin or planing -type ,in. one. or more ,operations, or these grooves may be cast or moulded if the material {of the platesean-rbe or .molfldeijor. instance,

under pressure. The bars themselves are preferabl y idrawn i to the ,desired 2 profile.

liigli-alsolshowsa,method oiiixing thabars in the id -p1at -by providin narrow r ov s .R. 4 5 pitched ior example-abouts. centimetre apart ,in ,the thicknessof theiplate T2 .011 its dorsal .side, namelythelsideoi the narrowerbase of thebars G the groovesRbeing disposed transversely to the grooves which receive ,the barsGaandbeing sufiicientlydeepso that the .bargrooves slightly penetrate the grooves .B,- w,hereby when the-bars .G 2 are :positioned in their ,grooves, portions of .the narrower-base of the bars lie exposed in the grooves B. After the bars=G have thus beeninserted-into their grooves, the plate T2 is rested on a slab with the grooves R uppermost and a suitable tool such ,as a small wheel is passed along the grooves R so as to ,roll or otherwise slightly deform theexposedportions of thebars out of line sufficiently to thereby lock-the bars to the plate. The direction of travel of .the tool from one groove ;R :to the next may bereversed vin order to ensure firm attachment of the bars.

,Another method would be tocast the material of the barsdn-the-material of the .plate, or conversely the material constitutes the plate :around the bars mounted on a temporary frame, if the melting points of the two materials permit. A grid of the-character shown in Fig. 5 may be=made '70 in this way.

Lined screens, used .for viewing the negatives or copies thereof are simple,photoeraphicscreens made by contact from an originalscreen of the same pitch therecording grid. This original screen may be made by copying by contact from ,enhanced.

. ,,As ,is also known, viewing under conditions ,o'ffthe highest luminosity is achieved by using, instead of. lined screens, screens made of a trans.- lucent material of suitable index which are cylindricallyfllenticulated or fluted by machining according to a suitable profile, the parallel axes of the diopters being of the same pitch as the bars of the recording grids.

: During' recording, and for satisfactoryviewing, it is necessary that the spacing-e between the rear side of the grid or lined screen and the emulsion surface should be rigorously fixed and maintained. According to which of the aboveijsuggested mountings (Figs. 3 to 5) is adoptedfor the grid and emulsion sup ort. and according to thej' nature of the support itself, this spacing may .befflassured by clamping either the edges only, orthe whole area, of the surfaces of the emulsion support and grid which face each other.

When the subject to be radiographed is thin. like a hand for instance, it may be placed in contact with a holder carrying the system T. P. The subject and the holder are ,then'kept. stationary, whilst the radiogenic source alone is displaced along a base equal to L+E, to ensure covering the elementary chambers under the angle 9 defined by p and e. The spatial construction obtained is superposed on the subject itself.

Any negative correctly recorded can be viewed in relief by viewing with the line joining the eyes placed transversely to the lines of the viewing screen (lined screen or lenticular screen). On the contrary. for viewing the distinct aspects of the radiographed subject as successively seen from the source moving along its base L, the line of the eyes must be parallel with the lines of the negative fitted with the lined or lenticular viewing screen, and the negative caused to move by translation in its plane perpendicularly to the direction of the lines, or caused to oscillate through an angle S2 in both directions around an axis parallel with the lines and the line joining the eyes, as is the practice for viewing the relative changes of aspect and sliding of the frontal planes of any subject photographed in relief.

It is possible to obtain photographs in relief identical with one another either by displacing the system T, P relatively to the projection point S, the two constituents T and P being fixedly spaced by e, or by placing these two constituents in close contact (6 0) and causing the grid T to slide transversely to its lines with a uniform movement on the surface of the emulsion of the support P during its unchanged displacement, the sliding of the grid being substantially equal to the width of one of the opaque bars of the grid during the period of total displacement of the projection point S. The direction in which the grid T slides on the emulsion support P is important, in order to obtain the correct relief and not a pseudoscopic relief.

A similar procedure may be adopted to obtain a radiograph in relief. Correct viewing of the developed or copied image takes place with a lined or lenticular viewing screen of pitch p 6. which slightly smaller than the pitch p of the recording "grid, in the ratio p h e if his the optimum viewing distance, 6 being the spacing adopted in the viewing holder between the lined viewing screen (or in thecase of a lenticularv'iewing screen, the plane containing the optical 'centres of the diopters of the screen) and'the; plane of the radiographic image. From the relations existing between L, E and p is deducedthe value of e which gives a satisfactory spatial scale of the aerial construction in relief. This "method also suggests a viewing method which'is a .corollary thereof, according to which a lined or lenticular screen of the same pitch p as the recording grid is made to slide in contact with the radiographic negative or copy therefrom in order to catch the successive aspects of the-radiographed subject, without imparting any other movement to the negative itself and without-the stationary observer or observers being obliged to fix their eyes on a line parallel with the lines'of the screen.

By a recording method in which the recording :grid'and' the emulsion support are mounted in i'contact (6:0), it is possible to obtain n+1 disvtinct'high definition radiological sections of the same "subject, provided the recording grid in contactnwith the emulsion occupies n+1 successive fixed positions (the opacity of the grid being measured by L f f n+1 where n is an integer), and. the amount of displacement of the grid transversely to its lines, from one record to the next, being equal to defined each time by the position of the section plane XX on the subject K. These successive sections are viewed by one of the methods above described; either one in which the lined or lenticular viewing screen, of suitable pitch 9 is mounted at the spacing e from the radiograph required by the size of p, whilst the observers eyes are parallel with the lines of the negative thus mounted and the system is displaced relatively to the observer, or one in which the viewing screen of pitch p is free to slide by exactly its pitch p in contact with the radiograph, and the observer or observers remain stationary relatively to the negative in the viewing positions, which are immaterial.

This invention also embraces the recording on the same negative of multiple radiographs of a subject, for instance in the course of its natural deformations (such as a human heart or a stomach), by keeping the radiogenic source and the plate or film carrying holder stationary during recording, the recording grid alone being moved in contact with the emulsion by the small displacement transversely to its lines which has 7A been discussed above. The result is observed by one of the methods described for viewing n+1 radiographic sections.

I claim: 1 1. A radiographic process for recording multiple radiographs (in the same negative of a stationary subject, comprising the steps'of arrangmg the subject between a point radiog'enic source and a photographically sensitised recording sur face arranging in close contact with said surfaceand between it and the subject a grid having'portions translucent to and linear-elements opaque to rays emitted from said source, expos iiig said recording" surface to rays impinging thereon from said source after passage through inent equal to the-width of one of said elements. S

' '2". A process for producing a radiograp'h capable of presenting different aspects of a radiographed section of a thin stationary subject whereby an impression of relief is obtained, comprising the steps of arranging the subject between a point source of X-rays and a photographically sensitised recording surface and in contact with One side of a grid having parallel equally spaced linear elements opaque to X-rays alternating with portion transparent to X-rays, the other side of the grid being near said recording surface and the subject being sufiiciently thin and the distance of the subject in contact with the grid being suchthat the section of the subject to be radiographed is arranged at substantiallythe same distance as said grid from said source and exposing said recording surface to the .X-ray beam from said source passing throughlsaid subject and, said transparent portions of said grid, while maintaining said subject, grid and recording surface stationary and translating saidsource transversely with respect to saidjopaque elements to cause contiguous elementary areas of said recording surface, each 0'1 widthequal to the pitch of said opaque elements and of length equal to the length of said opaque elements, to,be traversed simultaneously by the X-r'ay beamtr'aversing said transparent portions of, said grid. 7

. A. vn. JACQUES DE LASSUS s'r. GENIES.

REFERENCES CITED The following references are of record in'the file of this patent: 1

V STATES PATENTS Number.

Name Date v 758,117 Shook "1-- Apr. 26, 1904 1,547,376 Flarsheim. et al. July -28, 1925 1,566,130 Tichy et a1 r i Dec. 15, 1925 1,904,867 Kurtz Apr. 18, 1933 2 029300 Arfsten Feb. 4, 1936 2,150,932 McDonnell r .i Mar. 21, 1939 2,318,933 VWinnek i May 11,1943

' FOREIGN PATENTS Number Country Date 344,522 France "Nov. 4, 1907 449,213 Great Britain June 23, 1936 

